The mechanism of stimution of interferon production by a complexed polyribonucleotide

Fractionation of Aloe vera L. inner gel, purification and molecular profiling of activity

Products derived from the inner gel of the Aloe vera L. plant have demonstrated multiple clinical activities, and are used routinely to accelerate wound healing. However, typical of natural products, the complex nature of Aloe vera gels may contribute to diverse pharmacologic activities. Our focus on the hematopoietic activities of Aloe vera extracts is extended by these functional studies, which used purified fractions from Aloe vera gel and included a preliminary organ-specific in vitro molecular profile. Studies using a >99% pure carbohydrate fraction from Aloe vera extracts revealed increased hematopoietic and hematologic activity compared to the starting material. In addition, this fraction differentially regulated liver and lung cytokine mRNA levels, resulting in significant increases in message for hematopoietic cytokines [granulocyte colony stimulating factor (G-CSF) and stem cell factor (SCF)]. This profile of activity differed from another fraction obtained from Aloe vera, suggesting the potential for diverse pharmacologic activity. The molecular studies were undertaken using co-cultures of organ slices to limit the amount of purified material required. In summary, these studies revealed significant hematopoietic activity by both pharmacologic and molecular analysis using a >99% pure carbohydrate fraction from Aloe vera gels.

Effect of tumor burden and route of administration on the immunotherapeutic properties of polyinosinic-polycytidylic acid stabilized with poly-L-lysine in carboxymethyl cellulose [Poly(I,C)-LC]

We examined the immunomodulatory and therapeutic activities of poly(I,C)-LC. Mice received a subcutaneous (s.c.) injection of sufficient numbers of MBL-2 lymphoma cells to produce in 1 week either a high or low tumor burden. A week after tumor cell injection, poly(I,C)-LC treatment was initiated; the agent was administered intraperitoneally (i.p.) at 5 mg/kg twice a week or at 2.5 or 0.5 mg/kg every day or as an intravenous (i.v.) injection at 0.5, 0.05, or 0.005 mg/kg three times a week. Poly(I,C)-LC treatment significantly increased antitumor effector cell functions in a variety of organs (including spleen, lungs, and peritoneum), as shown by increased killing of MBL-2 cells in vitro and increased tumor cell killing by natural killer cells and macrophages. Furthermore, prolongation of survival correlated with peritoneal macrophage tumoricidal activity when poly(I,C)-LC was given i.p. and with pulmonary effector cell function (including natural killer, cytolytic T-lymphocyte and macrophage tumoricidal activity) when the agent was administered i.v.

Correlation of immunomodulatory and therapeutic activities of interferon and interferon inducers in metastatic disease

The mechanism of therapeutic activity of recombinant murine interferon-gamma (rMu IFN-gamma) and the IFN inducer polyinosinic-polycytidylic acid solubilized with poly-L-lysine in carboxy methyl cellulose (pICLC) in treating metastatic disease was investigated by comparing effector cell augmentation with therapeutic activity in mice bearing experimental lung metastases (B16-BL6 melanoma). Effector cell functions in spleen, peripheral blood, and lung (the organ with tumor) were tested after 1 and 3 weeks of rMu IFN-gamma or pICLC administration (intravenous, three times a week). In these studies, natural killer (NK), lymphokine-activated killer (LAK), cytolytic T lymphocytes (CTL) (against specific and nonspecific targets), and macrophage tumoricidal and tumoristatic activities were measured. rM IFN-gamma and pICLC had therapeutic activity and immunomodulatory activity in most assays of immune function examined. Specific CTL activity of pulmonary parenchymal mononuclear cells (PPMC), but not in splenocytes or peripheral blood lymphocytes (PBL), during week 3 and not during week 1, correlated with the therapeutic activity of rMu IFN-gamma and of pICLC. Macrophage tumoricidal activity in PPMC, but not in alveolar macrophages, also correlated with the therapeutic activity of rMu IFN-gamma, but the opposite was true for the therapeutic activity of pICLC. NK activity of PPMC, but not of splenocytes or PBL, during week 1 correlated with the therapeutic activity of pICLC; in contrast, NK activity at any site did not correlate with the therapeutic activity of rMu IFN-gamma. LAK activity at any site did not correlate with the therapeutic activity of either agent.

Cooperative interaction of multiple DNA elements in the human interferon-beta promoter

Analysis of promoter mutants and hybrids in permanently transformed murine L cells reveals several regulatory DNA sequence elements in the 5' flanking region of the human interferon-beta gene, which together constitute the inducible promoter. The elements consist almost exclusively of purine runs in the region -111 to -1. Deletion of single elements reduces the expression capacity drastically, whereas duplication leads to a synergism of inducible expression. These elements act together in a cooperative way to achieve high inducibility. Natural and mutant promoter fragments containing these elements impose inducibility on a heterologous promoter. However, typical enhancer activity in this system is not observed.

Natural cell-mediated cytotoxicity in rats. III. Effects of immunopharmacologic treatments on natural reactivity and on reactivity augmented by polyinosinic-polycytidylic acid

Treatment of rats with high doses of hydrocortisone, X-irradiation, or cyclophosphamide had a suppressive effect on natural cytotoxicity in vivo. However, when rats were given poly I:C after any of these agents, the levels of NK activity were similar to those in normal rats which had been given poly I:C alone. To explain these findings, we have postulated that a population of pre-NK cells, resistant to hydrocortisone, cyclophosphamide and X-irradiation was induced by poly I:C to become cytotoxic NK cells. Treatment of rats with silica, in doses that had no effect on proliferative responses of host lymphocytes to Con A in vitro, sharply diminished NK activity. With this agent, the boosting effect of poly I:C, although still detectable, was diminished. Since there is little if any indication that NK cells are phagocytic, these data suggest that phagocytes may play a role in maintaining high levels of NK activity in vivo and, further, may be involved in the mechanism by which natural cytotoxicity is boosted by poly I:C. Adult thymectomized rats had easily detectable levels of natural reactivity and the response to poly I:C was unimpaired, indicating a lack of thymic dependence for boosting as well as for spontaneous levels of NK activity.

A comparison of negatively and positively charged liposomes containing entrapped polyinosinic-polycytidylic acid for interferon induction in mice

Intravenous injection of negatively and positively charged liposomes containing entrapped poly(I)-poly(C) induced a vigorous interferon response in mice with serum titers of interferon reaching twenty times those observed with comparable dosages of free poly(I)-poly(C). The response did not persist over an extended time period as observed earlier for enhanced interferon production stimulated by positively charged liposomes containing the inducer. Both negatively and positively charged liposomes containing [14C]poly(I)-poly(C) were taken up chiefly by the liver when given intravenously. Negatively charged particles were concentrated somewhat preferentially by the spleen (7--9% of the dose compared to 4--6%). Less radioactivity was found in liver and spleen when negatively charged particles were given intraperitoneally than was the case when positively charged particles were injected by this route. Free [14C]poly(I)-poly(C) was extensively metabolized to low molecular weight materials within four hours of injection, while encapsulation of the polymer provided protection against in vivo degradation. When both preferential localization and protection were considered, from three to five times as much high molecular weight E114C]poly(I)-poly(C) was recovered from liver at four hours after intravenous injection when the compound was given in encapsulated form compared to free polymer. Similarly, for spleen, seven times and three times as much polymeric [14C]poly(I)-poly(C) was recovered following injection of negatively charged liposomes and positively charged liposomes respectively compared to free [14C]poly(I)-poly(C). At 48 h after an intravenous injection of positively charged liposomes, as much as four percent of the dose remained in high molecular weight form in the liver and one percent in the spleen. Following intraperitoneal injections, polymeric [14C]poly(I)-poly(C) recovered from the liver never exceeded 4.3% of the dose, showing that most of the radioactivity in the liver consisted of metabolites. These results suggest that elevated and prolonged production of interferon in animals treated with encapsulated inducer results from a combination of factors including preferential tissue location and protection of the inducer from hydrolytic cleavage.

Role of spleen in the interferon-lowering action of morphine

1. Polyinosinie-polycytidylic acid (Poly I:C) administered intraperitioneally to mice produced an increase in the level of interferon in the tissues of the spleen, liver, lung, and kidney. The level of circulating serum interferon also was increased by the polynucleotide. 2. The highest titer of interferon, presumably resulting from the greatest response to poly I:C was measured in the splenic tissue. 3. Morphine inhibited the poly I:C induced increase in all tissues and circulating serum. The decrease in interferon titer was similar in spleen and serum. 4. These results may indicate the serum level of interferon was more closely related and dependent upon events occuring in the spleen than in the other tissues.

Interferon induction by poly (I): poly (C) enclosed in phospholipid particles

Liposomes were prepared with phospholipids (sphingomyelin, lecithin, and phosphatidylethanolamine) in combination with cholesterol and charged lipids (dicetyl phosphate and stearylamine) and contained either poly(I):poly(C) or poly(I). Neutral and positively charged liposomes attached much better to L-929 cells in tissue culture than did negatively charged particles. Liposomes were toxic to L cells at relatively low concentrations, making the determination of antiviral activity induced by particles containing poly(I):poly(C) difficult to measure by the plaque reduction assay. When injected into mice, all of the liposomes containing poly(I):poly(C), except phosphatidylethanolamine liposomes, greatly potentiated and extended the serum interferon response of poly(I):poly(C). Lecithin and sphingomyelin liposomes given intravenously were ten times more effective than free poly(I):poly(C) in stimulating production of serum interferon. Sphingomyelin liposomes containing [(14)C]poly(I):poly(C) were 88% cleared from the bloodstream of mice by 3 min after intravenous injection. Most of the radioactivity (70%) was captured by the liver and remained there for at least 4 h. By 2 h, 7% of the radioactivity could be found in the spleen. Five percent of the radioactivity was found in the lungs at 30 min, with decreasing amounts thereafter. Small amounts of radioactivity were found in the muscle and kidneys. The spleen was shown to contain appreciable levels of interferon at 4 h, and low levels were found in the liver. Radioactivity accumulated slowly in the liver following an intraperitoneal injection of sphingomyelin liposomes containing [(14)C]poly(I):poly(C). By 4 h, 26% of the dose was recovered from the liver and 4.9% from the spleen, with small amounts in the lung, kidney, and omentum.

Variable response of human cells to polyinosinic-polycytidylic acid

Human cells derived from various organs of a single embryo responded variably to polyinosinic-polycytidylic acid with respect to induction of antiviral resistance and interferon.

In vivo release of previously cleared interferon by cycloheximide

The release of previously cleared interferon by cycloheximide was studied in the mouse. When cycloheximide was administered after either endogenous interferon stimulation or administration of exogenous interferon, the clearance of interferon from the blood stream was interrupted and a sharp rise in interferon titer occurred approximately 6 hr after cycloheximide administration followed by a rapid decline to low levels. This effect was observed with either interferon stimulated endogenously (by polyriboinosinic.polyribocytidylic acid), or homologous (mouse) or heterologous (rabbit) interferon administered exogenously. Serum protein concentrations also exhibited this rise and fall phenomenon after cycloheximide administration although the magnitude of the change in protein concentrations was less pronounced than that observed with interferon. Hematocrits, although elevated in mice receiving cycloheximide, did not exhibit this rise and fall phenomenon. Hence, cycloheximide administration leads to the release into the circulation of previously cleared interferon as well as other proteins.

Mouse Resistance Against Foot-and-Mouth Disease Virus Induced by Injections of Pyran

Mouse resistance to foot-and-mouth disease virus (FMDV) was induced by intraperitoneal injections of pyran copolymer. A biphasic pattern of protection occurred with greatest resistance 4 and 48 hr after injection of this polyanion. Viremia was not detectable in pretreated mice challenge-exposed with FMDV. Incubation of virus with pyran did not alter viral infectivity in mice or tissue culture. Serum interferon was demonstrated 1 and 2 days after pyran administration.

Regulation of cellular interferon production: enhancement by antimetabolites

Cycloheximide, at a protein-inhibitory concentration, when given to rabbit kidney cell cultures that had been exposed either to UV-irradiated Newcastle Disease virus or to a complex of polyinosinic and polycytidylic acids (poly I.poly C), enhanced the production of interferon. The enhancement was greater if, in addition to cycloheximide, the cells were also treated with actinomycin D. On the basis of these findings, a mechanism, consisting primarily of the production of a control protein which normally checks interferon production, is postulated for interferons stimulated by these two substances.